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    <title>graph_union</title>
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    <center>Scilab function</center>
    <div align="right">Last update : September 1996</div>
    <p>
      <b>graph_union</b> -  union of two graphs</p>
    <h3>
      <font color="blue">Calling Sequence</font>
    </h3>
    <dl>
      <dd>
        <tt>g2 = graph_union(g,g1)  </tt>
      </dd>
    </dl>
    <h3>
      <font color="blue">Parameters</font>
    </h3>
    <ul>
      <li>
        <tt>
          <b>g</b>
        </tt>: graph list</li>
      <li>
        <tt>
          <b>g1</b>
        </tt>: graph list</li>
      <li>
        <tt>
          <b>g2</b>
        </tt>: graph list of the new graph</li>
    </ul>
    <h3>
      <font color="blue">Description</font>
    </h3>
    <p>
      <tt>
        <b>graph_union</b>
      </tt> creates a new graph <tt>
        <b>g2</b>
      </tt>. The node set of <tt>
        <b>g2</b>
      </tt>
    is the union (in the usual sense) of the node sets of <tt>
        <b>g</b>
      </tt> and <tt>
        <b>g1</b>
      </tt>.
    <tt>
        <b>g2</b>
      </tt> has an edge for each edge of <tt>
        <b>g</b>
      </tt> and an edge for each edge of 
    <tt>
        <b>g1</b>
      </tt>.
    The edges of <tt>
        <b>g</b>
      </tt> and <tt>
        <b>g1</b>
      </tt> having the same endpoints are kept 
    and in this case <tt>
        <b>g2</b>
      </tt> has multiple edges.</p>
    <h3>
      <font color="blue">Examples</font>
    </h3>
    <pre>

ta=[1 1 2 2 2 3 4 5 5 7 8 8 9 10 10 10 10 10 11 12 13 13 13 14 15 16 16 17 17];
he=[2 10 3 5 7 4 2 4 6 8 6 9 7 7 11 13 13 15 12 13 9 10 14 11 16 1 17 14 15];
g=make_graph('foo',1,17,ta,he);
g('node_x')=[283 163 63 57 164 164 273 271 339 384 504 513 439 623 631 757 642];
g('node_y')=[59 133 223 318 227 319 221 324 432 141 209 319 428 443 187 151 301];
g('edge_color')=modulo([1:(edge_number(g))],15)+1;
g('node_diam')=[1:(g('node_number'))]+20;
g('node_name')=['A' 'B' 'C' 'D' 'E' 'F' 'G' 'H' 'I' 'J' 'K' 'L' 'M' 'N' 'O' 'P' 'Q'];
w=show_graph(g);
v=[7 8 9 10 11 12 13];
show_nodes(v);
g1=subgraph(v,'nodes',g);
show_graph(g1,'new');
v=[1 2 5 6 7 8 9 10];
netwindow(w);
show_nodes(v);
g2=subgraph(v,'nodes',g);
show_graph(g2,'new');
g=graph_union(g1,g2);
show_graph(g,'new');
 
  </pre>
    <h3>
      <font color="blue">See Also</font>
    </h3>
    <p>
      <a href="supernode.htm">
        <tt>
          <b>supernode</b>
        </tt>
      </a>,&nbsp;&nbsp;<a href="subgraph.htm">
        <tt>
          <b>subgraph</b>
        </tt>
      </a>,&nbsp;&nbsp;</p>
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